Thermoplastic elastomer composition and powder and molded article thereof

ABSTRACT

A thermoplastic elastomer composition comprising (a) 100 wt. parts of a polyolefin resin, (b) 5 to 250 wt. parts of an ethylene-α-olefin copolymer rubber in which the content of the α-olefin units is at least 50 wt. %, and (c) 0 to 500 wt. parts of an ethylene-α-olefin copolymer rubber in which the content of the α-olefin units is less than 50 wt. %. This composition can provide a molded article which is hardly whitened when it is bent, and has good flexiblity.

FIELD OF THE INVENTION

The present invention relates to a thermoplastic elastomer composition,and a powder and a molded article of the same.

PRIOR ART

Sheet-form molded articles having complicated uneven decorations such asgrains or stitches are used as skin materials of interior parts ofautomobiles and the like. As such molded articles, molded articles ofthermoplastic elastomers are proposed as substitutes for conventionalmolded articles of vinyl chloride resins (see, for example,JP-A-5-001183 and JP-A-5-005050). However, the molded articles ofthermoplastic elastomers have lower flexibility than those of vinylchloride resins, and tend to be whitened when they are bent. Thus, themolded articles of the thermoplastic elastomers are easily whitened atbent portions when they are removed from a mold in the molding processfor the production of molded articles or when they are preshaped beforethey are laminated onto substrates. Therefore, it is desired to providemolded articles of thermoplastic elastomers which are less whitened onbending.

SUMMARY OF THE INVENTION

The present inventors have made extensive study on thermoplasticelastomers which can provide molded articles which are less whitened onbending. As a result, it has been found that a thermoplastic elastomercomposition comprising a polyolefin resin and a specificethylene-α-olefin copolymer rubber in a specific ratio can provide amolded article which is hardly whitened, and the present invention hasbeen completed.

According to the first aspect, the present invention provides athermoplastic elastomer composition comprising

(a) 100 wt. parts of a polyolefin resin,

(b) 5 to 250 wt. parts of an ethylene-α-olefin copolymer rubber in whichthe content of the α-olefin units is at least 50 wt. %, and

(c) 0 to 500 wt. parts of an ethylene-α-olefin copolymer rubber in whichthe content of the α-olefin units is less than 50 wt. %.

According to the second aspect, the present invention provides a powdercomprising the above thermoplastic elastomer composition and having asphere-converted average particle size of 1.2 mm or less and a bulkspecific gravity of at least 0.38.

Such a powder is used in a powder molding method and can provide amolded article which has neither pinholes nor underfills and also goodflexibility so that it is hardly whitened when it is bent.

According to the third aspect, the present invention provides a moldedarticle comprising the above thermoplastic elastomer composition. Themolded article of the present invention is hardly whitened when it isbent.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view of a molding machine for powder molding,which comprises a container (2) for receiving the powder (3) of athermoplastic elastomer composition, and a mold (1) for powder slushmolding,

FIG. 2 is a plane view on the mold surface side of a mold for powderslush molding, and

FIG. 3 is a cross section of a molded article produced using the mold ofFIG. 2.

DETAILED DESCRIPTION OF THE INVENTION

The thermoplastic elastomer composition of the present inventioncomprises (a) 100 wt. parts of a polyolefin resin, (b) 5 to 250 wt.parts of an ethylene-α-olefin copolymer rubber in which the content ofthe α-olefin units is at least 50 wt. %, and (c) 0 to 500 wt. parts ofan ethylene-α-olefin copolymer rubber in which the content of theα-olefin units is less than 50 wt. %.

The polyolefin resin (a) is at least one crystallizable resin selectedfrom the group consisting of polymers and copolymers which comprise atleast one olefin. Examples of the olefin are ones having 2 to 8 carbonatoms such as ethylene, propylene, 1-butene, 1-hexene, 1-octene, and thelike. Examples of the polyolefin resin are polyethylene, polypropylene,polybutene-1, copolymers of propylene and an α-olefin other thanpropylene (e.g. 1-butene, etc.).

When the polyolefin resin (a) is a propylene-ethylene copolymer or apropylene-1-butene copolymer, the thermoplastic elastomer composition ofthe present invention can provide molded articles having excellentflexibility. Copolymers can be used, which are prepared bycopolymerizing at least two monomers selected from the group consistingof ethylene and α-olefins having 3 to 8 carbon atoms in two or morepolymerization steps. For example, a copolymer can be used, which isprepared by homopolymerizing propylene in the first step andcopolymerizing propylene with ethylene or an α-olefin other thanpropylene in the second step.

When a molded article is produced by a powder molding method using thepowder of the thermoplastic elastomer composition of the presentinvention, the polyolefin resin (a) has a melt flow rate (MFR) of from20 to 500 g/10 min., preferably from 50 to 300 g/10 min. when measuredaccording to JIS K-7210 at 230° C. under a load of 2.16 kgf, from theviewpoint of the strength of the produced molded articles.

The ethylene-α-olefin copolymer rubber (b) is at least one rubberselected from amorphous ethylene-α-olefin copolymers in which thecontent of the α-olefin units is at least 50 wt. %. Examples of theα-olefin are those having 3 to 8 carbon atoms such as propylene,1-butene, 1-hexene, 1-octene, etc. Among them, α-olefins having 4 to 8carbon atoms, in particular, 4 to 6 carbon atoms are preferable.

The content of the α-olefin units in the ethylene-α-olefin copolymerrubber (b) is preferably from 50 to 90 wt. %, more preferably from 60 to90 wt. %.

The ethylene-α-olefin copolymer rubber (b) may further contain, asmonomeric units, a non-conjugated diene having 5 to 12 carbon atoms suchas dicyclopentadiene, 2-methyl-2,5-norbornadiene,5-ethylidene-2-norbornene, 1,4-hexadiene, 1,6-octadiene, etc.; aromaticvinyl compounds having 8 to 12 carbon atoms such as styrene,α-methylsyrene, 2,5-dimethylstyrene, p-methylstyrene; and the like.

The content of the α-olefin units can be calculated from absorbances atpeaks assigned to the α-olefin units (for example, a peak due to thesymmetric deformation vibration of terminal methyl groups of short-chainbranches, or a peak due to the rocking vibration of methylene groups inthe branches) which are measured by an infrared spectrophotometry. Thismeasurement of the α-olefin unit content is described in, for example,(1) “POLYMER ANALYSIS HANDBOOK” (KOUBUNSHI BUNSEKI HANDOBUKKU), Chapter2, Section 2.2, pages 587-591 (1995) (edited by the Japan AnalyticalChemistry Society, published by KINOKUNIYA SHOTEN), and (2) “CHEMISTRYDOMAIN” (KAGAKU NO RYOIKI), Extra Issue No. 140 “INFRARED, RAMAN ANDVIBRATION [II] Present Situation and Future Prospects, pages 73-81(1983) (edited by Naomichi Tsuboi, et al., published by NANKODO).

The ethylene-α-olefin copolymer rubber (b) can be prepared bypolymerizing ethylene, α-olefin and other optional monomer using a metalcomplex as an polymerization initiator in the presence of a co-catalyst,as disclosed in JP-A-3-163088 and JP-A-5-194641.

Examples of a co-catalyst are aluminum compounds such asmethylaluminooxane, aluminum halides, aluminumalkyl halides,trialkylaluminums, etc.; and Lewis acids having a boron atom such astris(pentafluorophenyl)borane,triphenylcarbeniumtetrakis(pentafluorophenyl)borane, etc. Theco-catalysts maybe used singly or in a combination of two or morecompounds.

Examples of the metal complex are zirconium complexes such as(tert.-butylamide)dimethyl(η⁵-cyclopentadienyl)silane-zirconiumdichloride, etc.; and titanium complexes such as(tert.-butylamide)dimethyl(tetrametyl-η⁵-cyclopentadienyl)-silanetitaniumdichloride,(anilide)(dimethyl)(tetramethyl-η⁵-cyclopentadienyl)-silanetitaniumdichloride, etc. The metal complexes may be supported on a carrier suchas alumina, magnesium chloride, silica and the like.

Ethylene and an α-olefin are copolymerized usually in a solvent.Examples of the solvent are hydrocarbons such as hexane, heptane,toluene, ethylbenzene, xylene, and the like. The copolymerization may becarried out in the atmosphere of an inert gas such as nitrogen, argon,hydrogen, etc. under atmospheric pressure or reduced pressure. Apolymerization temperature is usually from −30 to +250° C.

The amount of the ethylene-α-olefin copolymer rubber (b) in thethermoplastic elastomer composition of the present invention is from 5to 250 wt. parts, preferably from 20 to 250 wt. parts, more preferablyfrom 50 to 250 wt. parts, in particular from 80 to 220 wt. parts, per100 wt. parts of the polyolefin resin (a).

When the amount of the ethylene-α-olefin copolymer rubber (b) is lessthan 5 wt. parts, the obtained molded articles lose flexibility andremarkably tend to be whitened when they are bent. When the amount ofthe copolymer rubber (b) exceeds 250 wt. parts, the surfaces of theobtained molded articles tend to have large tackiness.

The thermoplastic elastomer composition of the present invention maycontain up to 500 wt. parts of the ethylene-α-olefin copolymer rubber(c) per 100 wt. parts of the polyolefin resin (a). When theethylene-α-olefin copolymer rubber (c) is contained in the thermoplasticelastomer composition, the cold resistance (low-temperature impactresistance) of molded articles produced from such a composition can beimproved.

The ethylene-α-olefin copolymer rubber (c) is at least one copolymerselected from the group consisting of amorphous ethylene-α-olefincopolymers and amorphous ethylene-α-olefin-non-conjugated dienecopolymers, which have an α-olefin unit content of less than 50 wt. %.

Preferable examples of the α-olefin are ones having 3 to 10 carbon atomssuch as propylene, 1-butene, 3-methyl-pentene-1, 1-octene, 1-decene, andthe like. In particular, propylene and 1-butene are preferable.

Preferable examples of the non-conjugated diene are dicyclopentadiene,2-methyl-2,5-norbornadiene, ethylidenenorbornene, 1,4-hexadiene,cyclooctadiene, methylenenorbornene, 1,6-octadiene, and the like. Inparticular, ethylidenenorbornene is preferable.

Examples of the ethylene-α-olefin copolymer rubber (c) includeethylene-propylene copolymer rubbers, ethylene-1-butene copolymerrubbers, and ethylene-propylene-ethylidenenorbornene copolymer rubbers(EPDM). The thermoplastic elastomer composition of the present inventioncomprising EPDM can provide molded articles having excellent heatresistance and tensile properties.

The content of α-olefin units in the ethylene-α-olefin copolymer rubber(c) is preferably from 5 to 40 wt. %, more preferably from 10 to 35 wt.%, while the content of ethylene units is usually from 60 to 95 wt. %,preferably from 65 to 90 wt. %. The contents of the olefin and ethyleneunits can be measured by a ¹³C-NMR analysis, an infraredspectrophotometry, and the like.

When molded articles are produced by a powder molding method from thepowder of the thermoplastic elastomer composition of the presentinvention, the ethylene-α-olefin copolymer rubber (c) preferably has aMooney viscosity (ML₁₊₄(100°) ) of from 10 to 350, more preferably from15 to 300, when measured according to ASTM D-927-57T at 100° C., fromthe viewpoint of the strength of the obtained molded articles.

The amount of the ethylene-α-olefin copolymer rubber (c) in thethermoplastic elastomer composition of the present invention is usuallyfrom 0 to 500 wt. parts per 100 wt. parts of the polyolefin resin (a).The amount of the ethylene-α-olefin copolymer rubber (c) is preferablyfrom 5 to 400 wt. parts, more preferably from 10 to 250 wt. parts, fromthe viewpoint of the cold resistance (low-temperature impactresistance).

In the thermoplastic elastomer composition of the present invention, thepolyolefin resin (a), the ethylene-α-olefin copolymer rubber (b) and theethylene-α-olefin copolymer rubber (c) may be crosslinkedintermolecularly and/or intramolecularly. That is, the polyolefin resin(a) may be intermolecularly and/or intramolecularly crosslinked, theethylene-α-olefin copolymer rubber (b) may be intermolecularly and/orintramolecularly crosslinked, or the ethylene-α-olefin copolymer rubber(c) may be intermolecularly and/or intramolecularly crosslinked.Furthermore, the polyolefin resin (a) and the ethylene-α-olefincopolymer rubber (b), or the polyolefin resin (a) and theethylene-α-olefin copolymer rubber (c), or the ethylene-α-olefincopolymer rubber (b) and the ethylene-α-olefin copolymer rubber (c) maybe intermolecularly crosslinked. For example, the polyolefin resin (a)and/or the ethylene-α-olefin copolymer rubber (c) can be crosslinked bykneading them, and further dynamic crosslinking the kneaded mixture.

The dynamic crosslinking of the kneaded mixture can be carried out bykneading the mixture and a crosslinking agent while heating.

As a crosslinking agent, usually an organic peroxide such as2,5-dimethyl-2,5-di(tert.-butylperoxy)hexane, dicumyl-peroxide, etc. maybe used. The crosslinking agent is used in an amount of 1 wt. part orless, preferably from 0.1 to 0.8 wt. part, more preferably from 0.2 to0.6 wt. part, per 100 wt. parts of the total amount of the polyolefinresin (a), the ethylene-α-olefin copolymer rubber (b) and theethylene-α-olefin copolymer rubber (c).

In the case of the use of an organic peroxide as a crosslinking agent, athermoplastic elastomer composition, which provides molded articleshaving good heat resistance, can be obtained, when the dynamiccrosslinking is carried out in the presence of a crosslinking aid suchas a bismaleimide compound. In this case, the amount of the organicperoxide is usually 0.8 wt. part or less, preferably from 0.2 to 0.8 wt.part, more preferably from 0.4 to 0.6 wt. parts, per 100 wt. parts ofthe total amount of the polyolefin resin (a), the ethylene-α-olefincopolymer rubber (b) and the ethylene-α-olefin copolymer rubber (c).

The amount of the crosslinking aid is usually 1.5 wt. parts or less,preferably from 0.2 to 1 wt. part, more preferably from 0.4 to 0.8 wt.part, per 100 wt. parts of the total amount of the polyolefin resin (a),the ethylene-α-olefin copolymer rubber (b) and the ethylene-α-olefincopolymer rubber (c).

The crosslinking aid is added to the composition prior to the additionof the crosslinking agent. In general, the crosslinking aid is addedwhen the components (a), (b) and (c) are kneaded.

The polyolefin resin (a), the ethylene-α-olefin copolymer rubber (b) andthe ethylene-α-olefin copolymer rubber (c) can be crosslinked bykneading these components, a crosslinking agent and an optionalcrosslinking aid with a single- or twin-screw extruder while heating.

The dynamic crosslinking under the above conditions preferentiallycrosslinks intermolecularly and/or intramolecularly theethylene-α-olefin copolymer rubber (b) and the ethylene-α-olefincopolymer rubber (c), while the polyolefin resin (a) may beintermolecularly and/or intramolecularly crosslinked, or the polyolefinresin (a) and the ethylene-α-olefin copolymer rubber (b) may beintermolecularly crosslinked, or the polyolefin resin (a) and theethylene-α-olefin copolymer rubber (c) may be intermolecularlycrosslinked, or the ethylene-α-olefin copolymer rubber (b) and theethylene-α-olefin copolymer rubber (c) may be intermolecularlycrosslinked. The thermoplastic elastomer composition of the presentinvention can contain any types of crosslinked materials.

The thermoplastic elastomer composition of the present invention maycontain any additives in addition to the above main components. Examplesof the additives are mineral oil-based softening agents such asparaffinic process oils, phenol-based, sulfite-based,phenylalkane-based, phosphite-based, amine-based or amide-based heatstabilizers, age resistors (antioxidants), weather stabilizers,antistatic agents, metal soaps, lubricants such as waxes, internal moldrelease agents such as methylpolysiloxane, pigments, fillers, foamingagents, foaming aids, foam stabilizers, and the like. Among them, themineral oil-based softening agents are preferable, since they canimprove the melt flowability of the thermoplastic elastomer compositionof the present invention, and the thermoplastic elastomer compositioncontaining such a softening agent can provide molded articles havinggood flexibility.

When a mixture of the above ethylene-α-olefin copolymer rubber (c) andthe mineral oil-based softening agent, that is, an oil-extendedethylene-α-olefin copolymer rubber, is used in the production process ofthe thermoplastic elastomer composition of the present invention, goodprocessability can be attained in the kneading and dynamic crosslinkingprocesses.

The content of the mineral oil-based softening agent in the oil-extendedethylene-α-olefin copolymer rubber is usually 120 wt. parts or less,preferably from 30 to 120 wt. parts, per 100 wt. parts of theethylene-α-olefin copolymer rubber (c).

The thermoplastic elastomer composition of the present invention maycontain other polymer, insofar as the effects of the present inventionare not impaired, and examples of the other polymer are elastomericpolymers such as natural rubbers, butyl rubbers, cycloroprene rubbers,acrylonitrile-butandiene rubbers, hydrogenated acrylonitrile-butadienerubbers, epichlorohydrin rubbers, acrylic rubbers, etc.;ethylene-acrylic acid copolymers; ethylene-vinyl acetate copolymers andtheir saponified products; ethylene-methyl methacrylate copolymers;ethylene-glycidyl methacrylate-vinyl acetate copolymers; and the like.

The viscolasticity of the thermoplastic elastomer composition of thepresent invention may vary in a wide range in accordance with themolding conditions of the composition. When the thermoplastic elastomercomposition of the present invention is used to prepare a powder whichis used in the powder molding method and produced by a freeze-grindingmethod which will be explained below, the complex dynamic viscosityη*(1) of the composition measured at a frequency ω of 1 radian/sec. at250° C. is preferably 1.5×10⁵ poises or less, more preferably 5×10³poises or less, in particular 3×10³ poises or less from the viewpoint ofthe molding processability of the composition. The lower limit of η*(1)of the composition is usually 1×10² poises, preferably 3×10² poises,more preferably 5×10² poises.

Herein, a complex dynamic viscosity η*(ω) measured at a frequency ω andat 250° C. is calculated from a storage viscoelasticity G′ (ω) and aloss viscoelasticity G″ (ω) according to the following formula (1):

η*(ω)=(1/ω) [(G′(ω))²+(G″(ω))²]^(½)  (1)

When η*(1) exceeds 1.5×10⁵ poises, the thermoplastic elastomercomposition has insufficient melt flowability, and the processability ofthe composition in the powder molding method tends to deteriorate.

A Newtonian viscosity index n is 0.67 or less, preferably from 0.01 to0.35, more preferably from 0.03 to 0.25 from the viewpoint of themechanical strength of the molded articles. Here, a Newtonian viscosityindex n is calculated from the above complex dynamic viscosity η*(1) anda complex dynamic viscosity η*(100) measured at a frequency ω of 100radian/sec. at 250° C. according to the following formula (2):

n=[log η*(1)−log η*(100)]/2  (2)

When a thermoplastic elastomer composition is used in the production ofa powder by a solvent-treating method, a strand cutting method or adie-face cutting method, which will be explained below, the complexdynamic viscosity η*(1) of the composition is preferably 5×10⁴ poises orless, more preferably from 1×10² to 3×10³ poises, in particular from3×10² to 2×10³ poises from the viewpoint of the processability of thethermoplastic elastomer composition. The Newtonian viscosity index n ofsuch a thermoplastic elastomer composition is preferably 0.28 or less,more preferably from 0.01 to 0.25, in particular from 0.03 to 0.20, fromthe viewpoint of the mechanical strength of the produced moldedarticles.

The thermoplastic elastomer composition of the present invention can beprepared by kneading the polyolefin resin (a), the ethylene-α-olefincopolymer rubber (b) and optionally the ethylene-α-olefin copolymerrubber (c). When the ethylene-α-olefin copolymer rubber (c) is used,firstly the polyolefin resin (a) and the ethylene-α-olefin copolymerrubber (c) are kneaded, and then the ethylene-α-olefin copolymer rubber(b) is added and further kneaded.

Furthermore, the thermoplastic elastomer composition of the presentinvention, in which the polyolefin resin (a) and/or theethylene-α-olefin copolymer rubber (c) are intermolecularly and/orintramolecularly crosslinked, is usually prepared by dynamiccrosslinking the polyolefin resin (a) and the ethylene-α-olefincopolymer rubber (c), and then adding the ethylene-α-olefin copolymerrubber (b), followed by further kneading. Here, a single- or twin-screwextruder and the like can be used to knead the ethylene-α-olefincopolymer rubber (b).

Alternatively, the thermoplastic elastomer composition of the presentinvention can be-prepared by dynamic crosslinking the mixture of thepolyolefin resin (a), ethylene-α-olefin copolymer rubber (b) andethylene-α-olefin copolymer rubber (c).

The above methods provide the thermoplastic elastomer composition of thepresent invention in the form of a molten mixture.

The optional additives can be compounded by the use of the polyolefinresin (a), the ethylene-α-olefin copolymer rubber (b) or theethylene-α-olefin copolymer rubber (c) which contains such additives, orby compounding such additives to the mixture of the components (a), (b)and (c) in the course of kneading or dynamic crosslinking.

The thermoplastic elastomer composition of the present invention can beprocessed in the form of molded articles having various sizes and formsby a variety of molding methods. Molded articles produced from thethermoplastic elastomer composition of the present invention ischaracterized in that they are hardly whitened when they are bent. Forexample, the thermoplastic elastomer composition of the presentinvention can be molded in various types of molded articles by pressmolding, injection molding or extrusion molding a melt, for example, theabove molten mixture of the composition.

The forms and sizes of molded articles are not limited.

The thermoplastic elastomer composition of the present invention can beprocessed to obtain powders having various sizes and shapes, and suchpowders are used to produce molded articles such as sheets or films bypowder molding methods.

The above-described sphere-converted average particle size is preferably1.2 mm or less, more preferably from 0.15 to 1.0 mm from the viewpointof the easiness of fusion bonding of particles in the powder molding.When the particles are insufficiently fusion bonded, the molded articlesare apt to have pinholes or underfills.

The bulk specific gravity of the powder is preferably at least 0.38,more preferably from 0.38 to 0.65, in particular from 0.42 to 0.65 fromthe viewpoint of the easiness of adhesion of the powder to mold surfacesin the powder molding. When the powder is insufficiently adhered to themold surfaces, the molded articles are apt to have pinholes orunderfills.

Herein, a sphere-converted average particle size means a diameter of asphere having the same volume as the average volume of powder particles.The average volume (V) of powder particles is defined by the followingformula:

V=W/D

in which W is the total weight of randomly sampled 100 particles of athermoplastic elastomer composition powder, and D is a density of thethermoplastic elastomer composition.

The bulk specific gravity of a powder is defined and measured accordingto JIS K-6721.

Such a powder can be produced by various methods, which will beexplained below.

Freeze-grinding method:

A thermoplastic elastomer composition is cooled to a temperature lowerthan its glass transition temperature (usually −70° C. or less,preferably −90° C. or less) and then ground.

Solvent-treating method:

The powder of a thermoplastic elastomer composition, which is producedby the above freeze-grinding method, is stirred in a solvent having alow compatibility with the thermoplastic elastomer composition in thepresence of a dispersant and an emulsifier at a temperature higher thanthe melting point of the thermoplastic elastomer composition, preferablya temperature 30 to 50° C. higher than the melting point, and thencooled (see, for example, JP-A-62-280226). This method producesspherical particles.

Strand cutting method:

A molten thermoplastic elastomer composition is extruded through a dieinto an air to form strands, and then the strands are cooled and cut(see, for example, JP-A-50-149747).

Die-face cutting method:

A molten thermoplastic elastomer composition is extruded from a die intowater, and cut.

In the above solvent treating method, ethylene glycol, polyethyleneglycol, polypropylene glycol, or the like is used as a solvent in anamount of from 300 to 1,000 wt. parts, preferably from 400 to 800 wt.parts, per 100 wt. parts of the thermoplastic elastomer composition.

As a dispersant, an ethylene-acrylic acid copolymer, anhydrous silicicacid, titanium oxide, or the like is used in an amount of usually from 5to 20 wt. parts, preferably from 10 to 15 wt. parts, per 100 wt. partsof the thermoplastic elastomer composition.

As an emulsifier, polyoxyethylene sorbitan monolaurate, polyethyleneglycol monolaurate, sorbitan tristearate, or the like is used in anamount of usually from 3 to 15 wt. parts, preferably from 5 to 10 wt.parts, per 100 wt. parts of the thermoplastic elastomer composition.

In the strand cutting method, a die opening has a diameter of usuallyfrom 0.1 to 3 mm, preferably from 0.2 to 2 mm. The discharged amount ofthe thermoplastic elastomer composition from each die opening is usuallyfrom 0.1 to 5 kg/hr., preferably from 0.5 to 3 kg/hr. The haul-off rateof a strand is usually from 1 to 100 m/min., preferably from 5 to 50m/min. The cooled strand is cut in a length of usually 1.4 mm or less,preferably from 0.3 to 1.2 mm.

In the die-face cutting method, a die opening has a diameter of usuallyfrom 0.1 to 3 mm, preferably from 0.2 to 2 mm. The discharged amount ofthe thermoplastic elastomer composition from each die opening is usuallyfrom 0.1 to 5 kg/hr., preferably from 0.5 to 3 kg/hr. The temperature ofwater is usually from 30 to 70° C., preferably from 40 to 60° C.

The powders produced by the above solvent-treating method,strand-cutting method and die-face cutting method may be called“pellets”.

The powder of the thermoplastic elastomer composition can be used invarious powder molding methods such as a powder slush molding method, afluidized bed dipping method, an electrostatic coating method, a powderspray coating method, a rotational powder molding, and the like.

For example, the powder slush molding is carried out as follows:

The powder of a thermoplastic elastomer composition is supplied on themold surface of a mold which is heated at a temperature higher than themelt temperature of the thermoplastic elastomer composition, usuallyfrom 160 to 300° C., preferably from 210 to 270° C. The powder is heatedon the mold surface for a certain period of time, and powder particles,at least the surfaces of which are molten, are allowed to fuse together.After the certain period of time, non-fused powder particles arerecovered. If necessary, the mold carrying the fused thermoplasticelastomer composition is further heated. After that, the mold is cooled,and a formed sheet is removed from the mold. In such a method, the moldis heated by any method such as a gas heating furnace method, a heattransfer medium-circulation method, a dipping method in a heat transfermedium or hot fluidizing sand, a radiofrequency induction heatingmethod, and the like.

A heating time to fuse together the particles of the thermoplasticelastomer composition is fitly selected according to the sizes,thickness and the like of desired molded articles.

The molded articles of the present invention, which are produced fromthe thermoplastic elastomer composition of the present invention, havecharacteristics that they have good flexibility and are hardly whitenedwhen they are bent.

Foamed molded articles with good flexibility can be produced using thethermoplastic elastomer composition of the present invention whichcontains a foaming agent by various molding methods such as a powdermolding method, a press molding method, an extrusion molding method, aninjection molding method, and the like.

A foaming agent may be any conventional heat-decomposable foaming agent.Examples of such a heat-decomposable foaming agent are azo compoundssuch as azodicarbonamide, 2,2′-azobisisobutyronitrile,diazodiaminobenzene, etc.; sulfonylhydrazide compounds such asbenzenesulfonylhydrazide, benzene-1,3-sulfonylhydrazide,p-toluenesulfonylhydrazide, etd.; nitroso compounds such asN,N′-dinitrosopentamethylenetetraamine,N,N′-dinitroso-N,N′-dimethylterephthalamide, etc.; azide compounds suchas terephthalazide, etc.; carbonates such as sodium hydrogencarbonate,ammonium hydrogencarbonate, ammonium carbonate, etc.; and the like.Among them, azodicarbonamide is preferably used.

A foaming agent is compounded in the composition at a temperature oflower than the decomposition temperature of the foaming agent. Thethermoplastic elastomer composition of the present invention may containa foaming aid or a foam stabilizer together with a foaming agent.Alternatively, a foamed article can be produced by powder molding amixture of a foaming agent and the powder of the thermoplastic elastomercomposition of the present invention containing no foaming agent.

A molded article produced from the thermoplastic elastomer compositionof the present invention may be, for example, a two-layer molded articlewherein a foamed layer is laminated. Such a two-layer molded article canbe produced by a powder molding method which is disclosed in, forexample, JP-A-5-473, or bonding a molded article of the thermoplasticelastomer composition of the present invention and a foamed moldedarticle, which are separately produced, with an adhesive.

In the case of the production by a powder molding method, the layer ofthe thermoplastic elastomer composition of the present inventioncontaining no foaming agent is formed on a mold surface of a mold forpowder molding according to the above-described method. Then, the powderof a composition containing a foaming agent and a thermoplastic resin(or a thermoplastic elastomer) on the layer of the thermoplasticelastomer composition, and the powder particles are fused together toform a new layer. After that, the layer of the composition containingthe foaming agent is foamed to obtain a two-layer molded article.

A composite molded article having a structure consisting of a non-foamedlayer, a foamed layer and a non-foamed layer can be produced by ananalogous method to the above method. In this case, two non-foamedlayers may be the same or different.

Foaming agents used in the production of such two-ply molded articlesand composite molded articles may be the same heat-decomposable foamingagents as those used in the above.

Examples of a thermoplastic resin or elastomer to be contained in thecomposition which contains a foaming agent are vinyl chloride resins,polyolefin resins, olefinic thermoplastic elastomers and the like. Apolyethylene-based foamable composition, which is disclosed inJP-A-7-228720, may be used as the above-described composition containinga foaming agent.

The above foamed layer may comprise a polyurethane foam. In this case,it is preferable to increase adhesion properties between the layer ofthe thermoplastic elastomer composition of the present invention and thepolyurethane layer by pretreating the surface of the thermoplasticelastomer composition of the present invention with a primer such aschlorinated polyethylene, since the adhesion properties between thethermoplastic elastomer composition of the present invention andpolyurethane are usually not good.

The layer of a polyurethane foam can be formed by, for example,supplying a mixed liquid of a polyol, a polyisocyanate and a foamingagent between the molded article of the thermoplastic elastomercomposition of the present invention and a resin core material whichwill be explained below, and foaming the mixed liquid.

The molded article consisting of the thermoplastic elastomer compositionof the present invention, or the composite molded article comprising thelayer of the thermoplastic elastomer composition of the presentinvention and the foam layer can be used as a skin material for a resinmolded article (a resin core material) to produce a multilayer moldedarticle.

For example, the sheet of the thermoplastic elastomer composition of thepresent invention (a skin material) is laminated on the resin corematerial to form a two-layer molded article. Furthermore, the two-layermolded article consisting of the layer of the thermoplastic elastomercomposition of the present invention and the foam layer (a two-layerskin material) is laminated on a core material with the foam layerfacing the core material to form a three-lay er molded article.

Examples of the resins which constitute the core materials arethermoplastic resins such as polyolefin (e.g. polyethylene,polypropylene, etc.), and ABS resins (e.g.acrylonitrile-butadiene-styrene copolymer resins, etc.). Among them,polyolefin resins such as polypropylene are preferable.

The multilayer molded articles can be produced by supplying a moltenresin on one side of a skin material and pressurizing them. Thepressurization may be started after the completion of the resin supply.Alternatively, the pressurizatio n may be started before the completionof the resin supply and continued after the completion of the resinsupply. The pressurization may be effected by closing molds of a moldingmachine, or the supplying pressure of the resin.

For the production of multilayer molded articles, molding methods suchas injection molding, low pressure injection molding, low pressurecompression molding, and the like can be employed. For example, amolding machine comprising a pair of first and second molds which freelymove between an open position and closed position relatively is used,and a skin material comprising the layer of the thermoplastic elastomercomposition of the present invention is supplied into between the firstand second molds which are in the open position. Then, a molten resin issupplied in-between the skin material and one of the molds. After orduring the supply of the resin, the first and second molds arerelatively moved to pressurize the skin material and resin to produce amultilayer molded article.

When a skin material comprising the layer of the thermoplastic elastomercomposition of the present invention and a foam layer is used in theabove production method, a molten resin is supplied in-between the foamlayer of the skin material and the mold which faces the foam layer.

In the above production method, a molten resin can be supplied through aresin conduit which is provided in the wall of one mold. Alternatively,a resin supplying nozzle of a resin supplying apparatus, which is placedoutside a molding machine, is inserted in a skin material and one mold,and a molten resin is supplied through the nozzle. Then, the nozzle ispulled back from the molds.

The moving directions of the first and second molds are not limited.They can be moved vertically or horizontally.

The above-described methods are more preferable than an injectionmolding method in which a molten thermoplastic resin is suppliedin-between the first and second molds which are in the closed position,since the former methods can prevent the displacement of a skin materialand also avoid the damage of a skin material in comparison with theinjection molding method.

When a skin material which is produced by the above-mentioned powdermolding method is used, a mold used in the powder molding method can beused as a mold for the production of a multilayer molded article. Insuch as case, a mold for powder molding, which carries a skin materialformed by the powder molding method on the mold surface, is attached tothe above first mold. Then, the same steps as those described above arecarried out to produce a multilayer molded article. This method canproduce multilayer molded articles without damaging decorations whichhave been formed on the surface of the skin material by the powdermolding.

The above pair of molds may be, for example, a pair of male and femalemold halves which can move with the outer peripheral surface of thefirst mold half and the inner wall surface of the second mold half beingin slidingly contact each other. In this case, when a clearance betweenthe above outer peripheral surface and the above inner wall surface issubstantially the same as the thickness of a skin material, a multilayermolded article having the marginal portion of the skin material aroundthe article edges can be produced. When the marginal portion of the skinmaterial is folded back onto the back side of the multilayer moldedarticle, the molded article the edges of which are covered with the skinmaterial can be obtained.

Effects of the Invention

The thermoplastic elastomer composition of the present invention canprovide molded articles which have excellent flexibility and are noteasily whitened when they are bent.

EXAMPLES

The present invention will be explained in more detail by the followingexamples, which do not limit the scope of the invention in any way.

Evaluation methods

[1] Complex dynamic viscosity η*(1)

A storage viscoelasticity G′ (1) and a loss viscoelasticity G″ (1) of asample were measured using a dynamic analyzer (RDS-7700 manufactured byRheometrix) with a parallel plate mode, at an applied strain of 5%, asample temperature of 250° C. and a frequency ω of 1 radian/sec., andη*(1) was calculated from the measured storage and lossviscoelasticities according to the above formula (1).

[2] Newtonian viscosity index n

η*(100) was measured with the same sample as that used in themeasurement of η*(1) in the same manner as in the measurement of η*(1)except that a frequency o applied in the measurement of storage and lossviscoelasticities was changed to 100 radian/sec.

Then, a Newtonian viscosity index n was calculated from the calculatedη*(1) and η*(100) according to the above formula (2).

[3] Content of 1-butene units in ethylene-1-butene copolymers

(1) Construction of a calibration curve

Each of five mixtures of an ethylene-propylene copolymer (containing 73wt. % of ethylene units) and polybutene-1 in given ratios was heatpressed at 150° C. to form a film having a thickness of 0.05 mm. Witheach film, an absorbance ratio of a peak assigned to the ethylene units(wave number of 720 cm⁻¹) to a peak assigned to the 1-butene units (wavenumber of 772 cm⁻¹) was measured using an infrared spectrometer, andratios-of the 1-butene unit content to the total content of the ethyleneand 1-butene units of the five mixtures were plotted in a graph withsuch ratios on the abscissa and the absorbance ratios on the ordinate,and a calibration curve was drawn.

The mixtures of the ethylene-propylene copolymer and polybutene-1 wereprepared by dissolving both polymers in toluene in a single vessel,adding methanol to the solution to precipitate the polymers, recoveringthe precipitated polymer mixture and then drying it.

(2) Measurement of a 1-butene unit content

An ethylene-1-butene copolymer rubber was heated to a temperature higherthan its melting point and pressed to form a film having a thickness of0.05 mm. With this film, an absorbance ratio of a peak assigned to theethylene units to a peak assigned to the 1-butene units was measuredusing an infrared spectrometer, and a 1-butene unit content in theethylene-1-butene copolymer rubber was read from the calibration curve.

[4] Content of 1-hexene units in an ethylene-1-hexene copolymer rubber

An ethylene-1-hexene copolymer rubber was heat pressed at 150° C. toform a film having a thickness of 0.05 mm. With this film, an absorbanceat a peak assigned to the terminal methyl groups on the n-butyl branchesin the 1-hexene units was measured using an infrared spectrometer, andthen a ratio of the number of the terminal methyl groups on the n-butylbranches to the number of carbon atoms in the backbone of theethylene-1-hexene copolymer rubber, that is, the degree of branching,was calculated. From this degree of branching, the number of branchedmonomer units and the number of unbranched monomer units werecalculated, and then a 1-hexene unit content (wt. %) was calculated fromthese numbers.

A degree of branching was calculated according to the following formula:

Degree of branching (%)=[(f×A)/(t×d)]×100

wherein f is a coefficient (0.070 cm²/g), A is an absorbance, t is afilm thickness (cm), and d is the density (g/cm³) of anethylene-1-hexene copolymer rubber.

The coefficient f is cited from Usami, Takayama, et al. op. cit.

[5] Sphere-converted average particle size of a thermoplastic elastomercomposition

One hundred particles of a thermoplastic elastomer composition wererandomly sampled and their total weight was weighed. Then, an averagevolume per one particle was calculated from the total weight and thespecific gravity of the thermoplastic elastomer composition, and adiameter of a sphere having the same volume as the average volume wascalculated, and used as the sphere-converted average particle size ofthe powder of the thermoplastic elastomer composition.

[6] Bulk specific gravity of powder of a thermoplastic elastomercomposition

The bulk specific gravity of the powder of a thermoplastic elastomercomposition was measured according to JIS K-6721.

[7] Appearance of a molded article

With an obtained molded article, the presence of pinholes and underfillswas visually observed at edges of projections A (height: 7 mm, width: 5mm), B (height: 11 mm, width: 25 mm) and C (height: 15 mm, width: 25 mm)shown in FIG. 3, and evaluated according to the following criteria:

++: Neither pinholes nor underfills were observed on any edges of theprojections A, B and C.

+: Neither pinholes nor underfills were observed on any edges of theprojections A and B, but pinholes or underfills were observed on theedges of the projection C.

−: Neither pinholes nor underfills were observed on any edges of theprojection A, but pinholes or underfills were observed on the edges ofthe projections B and C.

−−: Pinholes or underfills were observed on all the edges of theprojections A, B and C.

[8] Whitening in the bending test of a molded article

A molded article was bent along its center line, and a load of 500 gf or1 kgf was applied to the bent article for one minute. Then, the load wasremoved, and the whitened state of the bent portion of the moldedarticle was visually observed and evaluated according to the followingcriteria:

+: Whitening was scarcely observed.

−: Whitening was slightly observed.

−−: Remarkable whitening was observed.

[9] Hardness of a molded article

A molded article was cut into pieces each having sizes of 1 cm×5 cm, andten pieces were laminated. Then, Shore A hardness of the laminate wasmeasured with a durometer-Shore A hadness meter.

Reference Example 1

An oil extended EPDM (ESPREN E670F manufactured by Sumitomo ChemicalCo., Ltd.) (50 wt. parts), which comprises EPDM (content of propyleneunits=28 wt. %; iodine value=12; ML₁₊₄ (100° C.)=242) and a mineraloil-based softener (DIANAPROCESS PW-380 manufactured by IDEMITSU KOSANCo., Ltd.) in a weight ratio of 1:1 and has ML₁₊₄ (100° C.) of 53, apropylene-ethylene random copolymer resin (content of ethylene units=5wt. %; MFR=90 g/10 min.) (50 wt. part), and a crosslinking aid (SUMIFINEBM, a bismaleimide compound manufactured by Sumitomo Chemical Co., Ltd.)(0.4 wt. part) were kneaded with a Banbury mixer for 10 minutes, andpelletized with an extruder and a pelletizer to obtain pellets having adiameter of 3 mm and a length of 6 mm.

The pellets (100 wt. parts) and2,3-dimethyl-2,5-di(tert.-butylperoxyno)hexane (SUNPEROX APOmanufactured by SANKEN KAKO KABUSHIKIKAISHA) (0.1 wt. part) were kneadedand dynamic crosslinked at 230° C. with a twin-screw extruder to obtaina composition having η*(1) of 5.2×10³ poises and n of 0.31. Then, thecomposition was extruded from the twin-screw extruder and pelletizedwith a pelletizer to obtain pellets having a diameter of 3 mm and alength of 6 mm.

Reference Example 2

Absolute toluene (1 liter) was charged in a 2 liter separable flaskwhich had been filled with nitrogen gas. Then, the flask was heated to30° C. while supplying a mixed gas of ethylene and 1-butene into theflask at an ethylene supply rate of 9 NL/min. and a 1-butene supply rateof 2.5 NL/min. After that, triisobutyl aluminum (0.25 g, 1.25 mmol) wasadded at 30° C. while supplying the above mixed gas and stirring, andthen(tert.-butylamide)dimethyl(tetramethyl-η⁵-cyclopentadienyl)silanetitaniumcichloride (0.018 g, 0.005 mmol), which had been prepared according tothe disclosure of JP-A-3-163088, was added.

The obtained mixture was stirred at 30° C. for15 minutes while supplyingthe above mixed gas, and thentriphenylcarbeniumtetrakis(pentafluorophenyl)borane (0.0023 g, 0.025mmol) was added, followed by further stirring at 30° C. for 30 minuteswhile supplying the above mixed gas.

Thereafter, methanol (20 ml) was added to terminate the polymerization,and the obtained mixture was poured into methanol (10 liters). Theprecipitate was collected by filtration and dried at 80° C. for 12 hoursunder reduced pressure to obtain an ethylene-1-butene copolymer rubber(156 g). The results of the evaluation of this ethylene-1-butenecopolymer rubber are shown in Table 1.

Reference Examples 3-6

An ethylene-1-butene copolymer rubber was prepared in the same manner asin Reference Example 2 except that a supply rate of 1-butene gas, apolymerization temperature and a polymerization time were changed asshown in Table 1. The results of the evaluation of eachethylene-1-butene copolymer rubber are shown in Table 1.

Reference Example 7

Absolute toluene (1 liter) was charged in a 2 liter separable flaskwhich had been filled with nitrogen gas, and an ethylene gas underatmospheric pressure was supplied at a rate of 2 NL/min. whilemaintaining the content in the flask at 0° C. Then, 1-hexene (126.2 g,1.5 mol) and triisobutyl aluminum (0.25 g, 1.25 mmol) were added to themixture, and further(tert.-butylamide)dimethyl(tetramethyl-η⁵-cyclopentadienyl)silanetitanium dichloride (0.018 g, 0.005 mmol), which had been preparedaccording to the disclosure of JP-A-3-163088, was added, while stirringat 0° C. After that, triphenylcarbeniumtetrakis(pentafluorophenyl)borane(0.0023 g, 0.025 mmol) was added, followed by further stirring at 0° C.for 5 minutes while supplying the ethylene gas.

Thereafter, methanol (20 ml) was added to terminate the polymerization,and the obtained mixture was poured into methanol (10 liters). Theprecipitate was collected by filtration and dried at 80° C. for 12 hoursunder reduced pressure to obtain an ethylene-1-hexene copolymer rubber(119 g). The results of the evaluation of this ethylene-1-butenecopolymer rubber are shown in Table 1.

TABLE 1 Ref. Ref. Ref. Ref. Ref. Ref. Ex. 2 Ex. 3 Ex. 4 Ex. 5 Ex. 6 Ex.7 Supply rate of 2.5 3.2 4.5 1.8 1.4 — 1-butene (NL/min.) Polymerization30 28 24 36 36 0 temp. (° C.) Polymerization 30 30 30 30 30 5 time(min.) 1-Butene unit 60 71 88 40 46 0 content (wt. %) 1-Hexene unit 0 00 0 0 70 content (wt. %) η*(1) (poises) 1.2 × 10⁴ 2.2 × 10³ 1.3 × 10³7.4 × 10³ 5.1 × 10³ 2 × 10² n 0.30 0.20 0.20 0.30 0.22 0.05

Example 1

The composition prepared in Reference Example 1 (100 wt. parts) and theethylene-1-butene copolymer rubber prepared in Reference Example 2 (5wt. parts) were kneaded with a twin-screw kneader at 190° C. to obtainthe molten mixture of a thermoplastic elastomer composition.

The molten mixture was press molded to obtain a sheet having a thicknessof 1 mm.

The results of the evaluation of the thermoplastic elastomer compositionwhich was molded, and the produced sheet are shown in Table 2.

Example 2

A thermoplastic elastomer composition and a sheet were produced in thesame manners as in Example 1 except that the amount of theethylene-1-butene copolymer rubber was changed to 10 wt. parts.

The results of the evaluation of the thermoplastic elastomercomposition, and the produced sheet are shown in Table 2.

Example 3

A thermoplastic elastomer composition and a sheet were produced in thesame manners as in Example 1 except that the amount of theethylene-1-butene copolymer rubber was changed to 20 wt. parts.

The results of the evaluation of the thermoplastic elastomercomposition, and the produced sheet are shown in Table 2.

Example 4

A thermoplastic elastomer composition and a sheet were produced in thesame manners as in Example 1 except that the ethylene-1-butene copolymerrubber prepared in Reference Example 3 (10 wt. parts) was used in placeof the ethylene-1-butene copolymer rubber which was prepared inReference Example 2 (5 wt. parts).

The results of the evaluation of the thermoplastic elastomercomposition, and the produced sheet are shown in Table 2.

Example 5

A thermoplastic elastomer composition and a sheet were produced in thesame manners as in Example 4 except that the amount of theethylene-1-butene copolymer rubber prepared in Reference Example 3 waschanged to 20 wt. parts.

The results of the evaluation of the thermoplastic elastomercomposition, and the produced sheet are shown in Table 2.

Example 6

A thermoplastic elastomer composition and a sheet were produced in thesame manners as in Example 1 except that the ethylene-1-butene copolymerrubber prepared in Reference Example 4 (10 wt. parts) was used in placeof the ethylene-1-butene copolymer rubber which was prepared inReference Example 2 (5 wt. parts).

The results of the evaluation of the thermoplastic elastomercomposition, and the produced sheet are shown in Table 2.

Example 7

A thermoplastic elastomer composition and a sheet were produced in thesame manners as in Example 6 except that the amount of theethylene-1-butene copolymer rubber prepared in Reference Example 4 waschanged to 20 wt. parts.

The results of the evaluation of the thermoplastic elastomercomposition, and the produced sheet are shown in Table 2.

Comparative Example 1

A thermoplastic elastomer composition and a sheet were produced in thesame manners as in Example 1 except that the ethylene-1-butene copolymerrubber prepared in Reference Example 5 (10 wt. parts) was used in placeof the ethylene-1-butene copolymer rubber which was prepared inReference Example 2 (5 wt. parts).

The results of the evaluation of the thermoplastic elastomercomposition, and the produced sheet are shown in Table 2.

Comparative Example 2

A thermoplastic elastomer composition and a sheet were produced in thesame manners as in Example 1 except that the ethylene-1-butene copolymerrubber prepared in Reference Example 6 (10 wt. parts) was used in placeof the ethylene-1-butene copolymer rubber which was prepared inReference Example 2 (5 wt. parts).

The results of the evaluation of the thermoplastic elastomercomposition, and the produced sheet are shown in Table 2.

Comparative Example 3

A thermoplastic elastomer composition and a sheet were produced in thesame manner as in Example 6 except that the ethylene-1-butene copolymerrubber prepared in Reference Example 6 (20 wt. parts) was used.

The results of the evaluation of the thermoplastic elastomercomposition, and the produced sheet are shown in Table 2.

Example 8

A propylene-ethylene random copolymer resin (ethylene unit content=4.5wt. %, MFR=228 g/10 min.) (66.7 wt. parts) and an ethylene-propylenecopolymer rubber (ESPREN V0141 manufactured by Sumitomo Chemical Co.,Ltd.; propylene unit content=27 wt. %, MFR=0.7 g/10 min.) (33.3 wt.parts) were kneaded with a twin-screw kneader at a shear rate of 1.2×10³sec.⁻¹ at 220° C. to obtain a composition having η*(1) of 1.8×10³ poisesand n of 0.12.

The obtained composition (100 wt. parts) and the ethylene-1-butenecopolymer rubber prepared in Reference Example 3 (66.7 wt. parts) werekneaded with a twin-screw kneader at 190° C. to obtain a moltenthermoplastic elastomer composition. Then, the composition was pressmolded to obtain a sheet having a thickness of 1 mm.

The results of the evaluation of the thermoplastic elastomercomposition, and the produced sheet are shown in Table 2.

TABLE 2 Ethylene-1-butene copolymer rubber Thermoplastic Whitening inthe 1-Butene elastomer bending test of unit content Amount*¹⁾composition molded article (wt. %) (wt. parts) η*(1) n 500 kgf 1 kgf Ex.1 60 10 3.1 × 10³ 0.21 − + Ex. 2 60 20 3.0 × 10³ 0.21 − + Ex. 3 60 403.1 × 10³ 0.21 + + Ex. 4 71 20 4.3 × 10³ 0.27 + + Ex. 5 71 40 2.1 × 10³0.17 + + Ex. 6 88 20 3.0 × 10³ 0.24 + + Ex. 7 88 40 3.0 × 10³ 0.24 + +C. Ex. 1 40 20 1.3 × 10⁴ 0.45 — — C. Ex. 2 46 20 1.0 × 10⁴ 0.40 — — C.Ex. 3 46 40 1.2 × 10⁴ 0.45 — — Ex. 8 71 100  1.9 × 10³ 0.14 + + Note:¹⁾An amount per 100 wt. parts of the ethylene-propylene random copolymerresin.

Example 9

A molten thermoplastic elastomer composition was prepared in the samemanner as in Example 3, and pelletized with a pelletizer to obtainpellets having a diameter of 3 mm and a length of 6 mm. The pellets werecooled to −120° C. and comminuted with a freeze-grinder to obtain thepowder of the thermoplastic elastomer composition. The powder had asphere-converted average particle size of 0.20 mm, and a bulk specificgravity of 0.32.

A nickel-electroformed mold (30 mm×30 mm, thickness of 3 mm) having agrain pattern on a mold surface was heated at 250° C., and the abovepowder (1 kg) was poured onto the mold surface. After 14 seconds,unfused powder was removed, and the mold carrying the fusedthermoplastic elastomer composition was heated in a heating furnace keptat 250° for 60 seconds. Then, the mold was pulled out from the heaterand cooled, and the shaped molded article was removed from the mold.

The molded article had a uniform thickness and no pinholes.

The results of the evaluation of the molded article are shown in Table3.

Example 10

A thermoplastic elastomer composition and a sheet were produced in thesame manners as in Example 9 except that the etylene-1-hexene copolymerrubber prepared in Reference Example 7 was used in place of theethylene-1-butene copolymer rubber prepared in Reference Example 2.

The results of the evaluation of the thermoplastic elastomer compositionand the sheet are shown in Table 3.

The thermoplastic elastomer composition had η*(1) of 1.2×10³ poises andn of 0.15.

TABLE 3 Ethylene-α-olefin copolymer rubber α-Olefin unit Whitening inthe bending content Amount*¹⁾ test of molded article α-Olefin (wt. %)(wt. parts) 500 gf 1 kgf Ex. 9 1-Butene 60 40 + + Ex. 10 1-Hexene 7040 + + Note: ¹⁾An amount per 100 wt. parts of the ethylene-propylenerandom copolymer resin.

Example 11

A propylene-ethylene random copolymer resin (ethylene unit content=4.5wt. %, MFR=228 g/10 min.) (100 wt. parts) and an ethylene-1-butenecopolymer rubber (1-butene unit content=71 wt. %, η*(1)=2.2×10³ poises,n=0.2) (50 wt. parts) were kneaded with a twin-screw kneader at 190° C.to obtain a thermoplastic elastomer composition having η*(1) of 1.4×10³poises and n of 0.13.

This composition was cooled to −100° C. with liquid nitrogen, andcomminuted with a freeze-grinder to obtain the powder of thethermoplastic elastomer composition. The powder had a sphere-convertedaverage particle size of 0.20 mm, and a bulk specific gravity of 0.33.

A nickel-electroformed mold (30 mm×30 mm, thickness of 3 mm) having agrain pattern on a mold surface was heated at 250° C., and the abovepowder (1 kg) was poured onto the mold surface. After 14 seconds,unfused powder was removed, and the mold carrying the fusedthermoplastic elastomer composition was heated in a heating furnace keptat 250° for 60 seconds. Then, the mold was pulled out from the heaterand cooled, and the shaped molded article was removed from the mold.

The results of the evaluation of the molded article are shown in Table4.

Example 12

A thermoplastic elastomer composition having η*(1) of 5×10³ poises and nof 0.18 was prepared in the same manner as in Example 11 except that 200wt. parts of the ethylene-1-butene copolymer rubber was used. The powderof this composition was prepared and then a molded article was producedin the same manners as in Example 11.

The results of the evaluation of the molded article are shown in Table4.

Example 13

A thermoplastic elastomer composition having η*(1) of 3×10³ poises and nof 0.04 was prepared in the same manner as in Example 11 except that 100wt. parts of an ethylene-1-hexene copolymer rubber (1-hexene unitcontent=70 wt. %, η*(1)=2×10² poises, n=0.03) was used. The powder ofthis composition was prepared and then a molded article was produced inthe same manners as in Example 11.

The results of the evaluation of the molded article are shown in Table4.

Comparative Example 4

An oil extended EPDM (ESPREN E670F manufactured by Sumitomo ChemicalCo., Ltd.) (50 wt. parts), which comprises EPDM (content of propyleneunits=28 wt. %; iodine value=12; ML₁₊₄(100° C.)=242) and a mineraloil-based softener (DIANAPROCESS PW-380 manufactured by IDEMITSU KOSANCo., Ltd.) in a weight ratio of 1:1 and has ML₁₊₄(100° C.) of 53, apropylene-ethylene random copolymer resin (content of ethylene units=4.5wt. %; MFR=90 g/10 min.) (50 wt. part), and a crosslinking aid (SUMIFINEBM, a bismaleimide compound manufactured by Sumitomo Chemical Co., Ltd.)(0.6 wt. part) were kneaded with a Banbury mixer for 10 minutes, andpelletized with an extruder and a pelletizer to obtain pellets having adiameter of 3 mm and a length of 6 mm).

The pellets (100 wt. parts) and2,3-dimethyl-2,5-di(tert.-butylperoxyno)hexane (SUNPEROX APOmanufactured by SANKEN KAKO KABUSHIKIKAISHA) (0.4 wt. part) were kneadedand dynamic crosslinked at 200° C. and a shear rate of 1.2×10³ sec.⁻¹with a twin-screw extruder to obtain a composition having η*(1) of1.5×10³ poises and n of 0.25. Then, the composition was cooled to −120°C. with liquid nitrogen, and comminuted with a freeze-grinder to obtaina powder having a sphere-converted average particle size of 0.20 mm anda bulk specific gravity of 0.30.

A molded article was produced in the same manner as in Example 11 exceptthat the above obtained powder was used.

The results of the evaluation of the molded article are shown in Table4.

TABLE 4 Whitening in the Shore A bending test of hardness molded articleof molded 500 gf 1 kgf article Ex. 11 + + 90 Ex. 12 + + 81 Ex. 13 + + 81C. Ex. 4 — — 92

Example 14

<Preparation of the powder of a thermoplastic elastomer composition>

The pellets of a composition which was prepared in the same manner as inComparative Example 4 (100 wt. parts) and an ethylene-1-butene copolymerrubber (1-butene unit content=71 wt. %, η*(1)=2.2×10³ poises, n=0.2) (10wt. parts) were supplied in an extruder having a diameter of 30 mm andkneaded at 160° C. The formed thermoplastic elastomer composition wasextruded through a die having a discharging opening diameter of 1.0 mmat a discharging rate of 1 kg/hr. per one discharging opening, and theextruded composition was hauled off at a rate of 32 m/min. and thencooled to obtain strands having a diameter of 0.8 mm. The strands werecut with a pelletizer to obtain a powder having a sphere-convertedaverage particle size of 0.91 mm and a bulk specific gravity of 0.465.

The thermoplastic elastomer composition obtained by kneading had η*(1)of 1.7×10³ poises and n of 0.21.

<Production of a molded article by powder slush molding>

The above obtained powder was power slush molded with a molding machine,the schematic view of which is shown in FIG. 1.

Firstly, the powder (3) was supplied into a container (2). Next, thecontainer (2) and a mold (1) were mated and fixed so that theperipheries of the openings of the container and mold were in closecontact with each other.

The mold (1) had, on its mold surface, three depressions as shown inFIG. 2, that is a depression “a” having a depth of 7 mm, a depression“b” having a depth of 11 mm, and a depression “c” having a depth of 15mm. The opening of each depression was a square having a side length of25 mm. The whole mold surface of the mold (1) had a grain pattern. Thetemperature of the mold (1) was 250° C.

Immediately after fixing the container (2) and the mold (1), they wererotated with a single-axis rotating apparatus by 180 degrees around arotation axis (4) to supply the powder (3) onto the mold surface of themold (1). Then, the fixed container (2) and mold (1) were oscillatedtwice at an amplitude of 45 degrees around the rotation axis (4) over 15seconds to melt the powder (3) and adhere the molten powder (3) to themold surface of the mold (1). After that, the fixed container (2) andmold (1) were again rotated by 180 degrees so that they returned to theoriginal position, and a portion of the powder (3) which was not adheredto the mold surface of the mold (1) was recovered to the container (2).

Thereafter, the mold (1) to which the fused powder (3) was adhered wasdetached from the container (2), heated in an oven at 250° C. for 2minutes, and cooled. Then, the molded article (5) was removed from themold (1).

The obtained molded article (5) had a thickness of 1.2 mm and threeprojections, that is, the projection A having a height of 7 mm, theprojection B having a height of 11 mm, and the projection C having aheight of 15 mm. The root portion of each projection was a square havinga side length of 25 mm.

The grain pattern formed on the mold surface of the mold (1) was exactlytransferred to the surface of the molded article which was in contactwith the mold surface of the mold (1). The cross section of this moldedarticle is shown in FIG. 3.

The results of the evaluation of the powder and the molded article areshown in Table 5.

Example 15

A molded article was produced in the same manner as in Example 14 exceptthat, in the production of the powder of the thermoplastic elastomercomposition, the discharging rate of the composition from the die waschanged to 0.8 kg/hr., and the haul-off rate was changed to 35 m/min.The powder used for the production of the molded article had asphere-converted average particle size of 0.94 mm, and a bulk specificgravity of 0.460.

The results of the evaluation of the molded article are shown in Table5.

Example 16

A molded article was produced in the same manner as in Example 14 exceptthat, in the production of the powder of the thermoplastic elastomercomposition, the haul-off rate was changed to 14 m/min. The powder usedfor the production of the molded article had a sphere-converted averageparticle size of 1.25 mm, and a bulk specific gravity of 0.470.

The results of the evaluation of the molded article are shown in Table5.

Example 17

A molded article was produced in the same manner as in Example 14 exceptthat an ethylene-1-hexene copolymer rubber (1-hexene unit content=70 wt.%, η*(1)=1×10² poises, n=0.03) was used. The powder used for theproduction of the molded article had a sphere-converted average particlesize of 0.92 mm, and a bulk specific gravity of 0.460. The thermoplasticelastomer composition constituting the powder had η* of 1.2×10³ poisesand n of 0.15.

The results of the evaluation of the molded article are shown in Table5.

Example 18

The pellets of a kneaded mixture, which was prepared in the same manneras in Comparative Example 4 (100 wt. parts), and an ethylene-1-butenecopolymer rubber (1-butene unit content=71 wt. %, η*(1)=2.2×10³ poises,n=0.2) (10 wt. parts) were supplied into a twin-screw extruder andkneaded at 200° C. Then, the formed thermoplastic elastomer compositionwas extruded from the extruder, and cut with a cutter to obtain pellets.The thermoplastic elastomer composition had η*(1) of 1.7×10³ poises andn of 0.21.

The pellets of the thermoplastic elastomer composition were cooled to−100° C. with liquid nitrogen, and comminuted to obtain a powder whichpassed through the 32 mesh (opening: 500 μm×500 μm) of the Tylerstandard sieve. The powder had a sphere-converted average particle sizeof 0.20 mm and a bulk specific gravity of 0.290.

A molded article was produced in the same manner as in Example 14 exceptthat the above powder was used.

The results of the evaluation of the powder and the molded article areshown in Table 5.

Example 19

A composition prepared in the same manner as in Example 8 (100 wt.parts), and an ethylene-1-butene copolymer rubber (1-butene unitcontent=71 wt. %; η*(1)=2.2×10³ poises; n=0.2) (66.7 wt. parts) weresupplied into an extruder having a diameter of 30 mm and kneaded at 160°C. The formed thermoplastic elastomer composition was extruded through adie having a discharging opening diameter of 1.0 mm at a dischargingrate of 0.8 kg/hr. per one discharging opening, and the extrudedcomposition was hauled off at a rate of 35 m/min. and then cooled toobtain strands having a diameter of 0.8 mm. The strands were cut with apelletizer to obtain a powder having a sphere-converted average particlesize of 0.88 mm and a bulk specific gravity of 0.460.

The thermoplastic elastomer composition obtained by kneading had η*(1)of 2×10³ poises and n of 0.14.

Then, a molded article was produced in the same manner as in Example 14except that the above powder was used.

The results of the evaluation of the powder and the molded article areshown in Table 5.

Comparative Example 5

A kneaded composition prepared in the same manner as in ComparativeExample 4 (100 wt. parts) was supplied into an extruder having adiameter of 30 mm and kneaded at 160° C. Then, the composition wasextruded through a die having a discharging opening diameter of 1.0 mmat a discharging rate of 1 kg/hr. per one discharging opening, and theextruded composition was hauled off at a rate of 32 m/min. and thencooled to obtain strands having a diameter of 0.8 mm. The strands werecut with a pelletizer to obtain a powder having a sphere-convertedaverage particle size of 0.90 mm and a bulk specific gravity of 0.450.

Then, a molded article was produced in the same manner as in Example 14except that the above powder was used.

The results of the evaluation of the powder and the molded article areshown in Table 5.

Comparative Example 6

The pellets of a kneaded composition, which was prepared in the samemanner as in Comparative Example 4, were cooled to −100° C. with liquidnitrogen, and comminuted to obtain a powder which passed through the 32mesh of the Tyler standard sieve. The powder had a sphere-convertedaverage particle size of 0.18 mm and a bulk specific gravity of 0.293.

A molded article was produced in the same manner as in Example 14 exceptthat the above powder was used.

The results of the evaluation of the powder and the molded article areshown in Table 5.

TABLE 5 Sphere- converted Whitening in the Discharging Haul-off averageBulk Appearance Hardness bending test of rate rate particle specific ofmolded of molded molded article (kg/hr.) (m/min.) size (mm) gravityarticle article 500 gf 1 kgf Ex. 14 1 32 0.91 0.465 ++ 88 + + Ex. 15 0.835 0.94 0.460 ++ 88 + + Ex. 16 1 32 0.92 0.460 ++ 88 + + Ex. 17 1 141.25 0.470 − 88 + + Ex. 18 — — 0.20 0.290 − 88 + + Ex. 19 0.8 35 0.880.460 ++ 84 + + C. Ex. 5 0.8 30 0.90 0.450 − 92 −− −− C. Ex. 6 — — 0.180.293 − 92 −− −−

Example 20

<Preparation of the powder of a thermoplastic elastomer composition>

A propylene-ethylene random copolymer (ethylene unit content=4.5 wt. %;MFR=228 g/10 min.) (100 wt. parts) and an ethylene-1-butene copolymerrubber (1-butene unit content=71 wt. %) (100 wt. parts) were suppliedinto an extruder having a diameter of 30 mm and kneaded at 160° C. Theformed thermoplastic elastomer composition was extruded through a diehaving a discharging opening diameter of 1.0 mm at a discharging rate of1 kg/hr. per one discharging opening, and the extruded composition washauled off at a rate of 32 m/min. and then cooled to obtain strandshaving a diameter of 0.8 mm. The strands were cut with a pelletizer toobtain a powder having a sphere-converted average diameter of 0.91 mmand a bulk specific gravity of 0.460.

The above thermoplastic elastomer composition had η*(1) of 1.4×10³poises and n of 0.13.

<Production of a molded article by powder slush molding>

A molded article was produced in the same manner as in Example 14 exceptthat the above powder was used.

The results of the evaluation of the molded article are shown in Table6.

Example 21

The powder of a thermoplastic elastomer composition was prepared in thesame manner as in Example 20 except that the amount of theethylene-1-butene copolymer rubber was changed to 200 wt. parts. Thispowder had a sphere-converted average particle size of 0.94 mm and abulk specific gravity of 0.450.

The thermoplastic elastomer composition had η*(1) of 1.8 ×10³ poises andn of 0.15.

A molded article was produced in the same manner as in Example 20 exceptthat the above powder was used.

The results of the evaluation of the molded article are shown in Table6.

Example 22

A molded article was produced in the same manner as in Example 20 exceptthat an ethylene-1-hexene copolymer rubber (1-hexene unit content=70 wt.%; η*(1)=2×10² poises; n=0.03) was used in place of theethylene-1-butene copolymer rubber.

The powder used in the production of the molded article had asphere-converted average particle size of 0.93 mm and a bulk specificgravity of 0.458, while the thermoplastic elastomer compositionconstituting the powder had η*(1) of 3×10² poises and n of 0.04.

The results of the evaluation of the molded article are shown in Table6.

Example 23

The powder of a thermoplastic elastomer composition was prepared in thesame manner as in Example 20 except that the haul-off rate of thethermoplastic elastomer composition from the die was changed to 14m/min.

The powder has a sphere-converted average particle size of 1.25 mm and abulk specific gravity of 0.450.

A molded article was produced in the same manner as in Example 20 exceptthat the above powder was used.

The results of the evaluation of the molded article are shown in Table6.

Example 24

A propylene-ethylene random copolymer resin (ethylene unit content=4.5wt. %; MFR=228 g/10 min.) (100 wt. parts) and an ethylene-1-butenecopolymer rubber (1-butene unit content=71 wt. %) (100 wt. parts) weresupplied into a twin-screw extruder and kneaded at 200° C. to obtain athermoplastic elastomer composition having η*(1) of 1.4×10³ poises and nof 0.13.

This composition was extruded from the same twin-screw extruder as usedin the above step, and cut with a cutter to obtain pellets of thecomposition having a diameter of 3 mm and a length of 6 mm.

Then, the pellets were cooled to −100° C. with liquid nitrogen andcomminuted to obtain a powder which passed through the 32 mesh of theTyler standard sieve. The powder had a sphere-converted average particlesize of 0.20 mm and a bulk specific gravity of 0.270.

A molded article was produced in the same manner as in Example 20 exceptthat the above powder was used.

The results of the evaluation of the molded article are shown in Table6.

Comparative Example 7

The pellets of a thermoplastic elastomer composition having η*(1) of1.5×10³ poises and n of 0.25 were prepared in the same manner as inComparative Example 4.

The pellets were supplied into an extruder having a diameter of 30 mmand kneaded at 160° C. The formed thermoplastic elastomer compositionwas extruded through a die having a discharging opening diameter of 1.0mm at a discharging rate of 1 kg/hr. per one discharging opening, andthe extruded composition was hauled off at a rate of 32 m/min. and thencooled to obtain strands having a diameter of 0.8 mm. The strands werecut with a pelletizer to obtain a powder having a sphere-convertedaverage diameter of 0.91 mm and a bulk specific gravity of 0.450.

A molded article was produced in the same manner as in Example 20 exceptthat the above powder was used.

The results of the evaluation of the molded article are shown in Table6.

Comparative Example 8

The pellets of a thermoplastic elastomer composition, which was preparedin the same manner as in Comparative Example 7, were cooled to −100° C.and comminuted to obtain a powder which passed through the 32 mesh ofthe Tyler standard sieve. The powder had a sphere-converted averageparticle size of 0.18 mm and a bulk specific gravity of 0.293.

A molded article was produced in the same manner as in Example 20 exceptthat the above powder was used.

The results of the evaluation of the molded article are shown in table6.

TABLE 6 Sphere- converted Whitening in the Discharging Haul-off averageBulk Appearance Hardness bending test of rate rate particle specific ofmolded of molded molded article (kg/hr.) (m/min.) size (mm) gravityarticle article 500 gf 1 kgf Ex. 20 1 32 0.91 0.460 ++ 88 + + Ex. 21 132 0.94 0.450 ++ 81 + + Ex. 22 1 32 0.93 0.458 ++ 87 + + Ex. 23 1 141.25 0.450 − 88 + + Ex. 24 — — 0.20 0.270 − 88 + + C. Ex. 7 0.8 30 0.910.450 ++ 92 −− −− C. Ex. 8 — −− 0.18 0.293 − 92 −− −−

What is claimed is:
 1. A thermoplastic elastomer composition comprising:a) 100 wt. parts of a polyolefin resin, b) 5 to 250 wt. parts ofethylene-α-olefin copolymer rubber in which the content of the α-olefinunits is 60-90 wt. %, wherein the wt. percent is with respect to theweight of the ethylene-α-olefin copolymer rubber, and c) 5 to 400 wt.parts of an ethylene-α-olefin copolymer rubber in which the content ofthe α-olefin units is 5 to 40 wt. %, wherein the wt. % is with respectto the weight of the ethylene-α-olefin copolymer rubber.
 2. Athermoplastic elastomer composition according to claim 1, wherein anα-olefin in said ethylene-α-olefin copolymer (b) is an α-olefin having 4to 8 carbon atoms.
 3. A thermoplastic elastomer composition according toclaim 1, wherein said ethylene-α-olefin copolymer rubber (b) is anethylene-1-butene copolymer rubber or an ethylene-1-hexene copolymerrubber.
 4. A thermoplastic elastomer composition according to claim 1,wherein said ethylene-α-olefin copolymer rubber (c) is anethylene-α-olefin-non-conjugated diene copolymer rubber.
 5. Athermoplastic elastomer composition according to claim 1, which has acomplex dynamic viscosity η*(1) of 1.5×10⁵ poises or less, when measuredat 250° C. and a frequency of 1 radian/sec.
 6. A thermoplastic elastomercomposition according to claim 1, which has a Newtonian viscosity indexn of 0.67 or less, which is calculated from a complex dynamic viscosityη*(1) and a complex dynamic viscosity η*(100) measured at 250° C. and afrequency of 100 radian/sec., according to the following formula: n=[logη*(1)−log η*(100)]/2.
 7. A thermoplastic elastomer composition accordingto claim 1, which has η*(1) of 1.5×10⁵ poises or less, and n of 0.67 orless.
 8. A thermoplastic elastomer composition according to claim 1,wherein at least one polymer selected from the group consisting of saidpolyolefin resin (a), said ethylene-α-olefin copolymer rubber (b) andsaid ethylene-α-olefin copolymer rubber (c) is intermolecularly and/orintramolecularly crosslinked.
 9. A thermoplastic elastomer compositionaccording to claim 1, which further comprises a foaming agent.
 10. Apowder comprising a thermoplastic elastomer composition as claimed inclaim 1, which has a sphere-converted average particle size of 1.2 mm orless, and a bulk specific gravity of at least 0.38.
 11. A powderaccording to claim 10, wherein said thermoplastic elastomer compositionhas η*(1) of 1.5×10⁵ poises or less, and n of 0.67 or less.
 12. A powderaccording to claim 10, wherein an α-olefin in the ethylene-α-olefincopolymer (b) contained in said thermoplastic elastomer composition isan α-olefin having 4 to 8 carbon atoms.
 13. A powder according to claim10, wherein said ethylene-α-olefin copolymer rubber (b) contained insaid thermoplastic elastomer composition is an ethylene-1-butenecopolymer rubber or an ethylene-1-hexene copolymer rubber.
 14. A powderaccording to claim 10, which is prepared by a solvent-treating method, astrand cutting method or a die-face cutting method.
 15. A molded articlecomprising a thermoplastic elastomer composition as claimed in claim 1.16. A molded article according to claim 15, which is produced by pressmolding.
 17. A mold article according to claim 15, which is produced bypower-slush molding a powder of said thermoplastic elastomer compositionhaving a sphere-converted average particle size of 1.2 mm or less, and abulk specific gravity of at least 0.38.
 18. A molded article accordingto claim 15, which is a foamed molded article.
 19. A multilayer moldedarticle comprising at least one layer formed from a thermoplasticelastomer composition as claimed in claim
 1. 20. A multilayer moldedarticle according to claim 19, which further comprises a core layer of athermoplastic resin.
 21. The thermoplastic elastomer compositionaccording to claim 1, wherein the amounts of ethylene-α-olefin copolymerrubbers (b) and (c) are 50 to 250 wt. parts and 10 to 250 wt. parts,respectively.